Radioactive Materials (OCR)
The structure of the atom ELECTRON negative, mass nearly nothing NEUTRON neutral, same mass as proton ( 1 ) PROTON positive, same mass as neutron ( 1 )
Isotopes An isotope is an atom with a different number of neutrons: Notice that the mass number is different. How many neutrons does each isotope have? Each isotope has 8 protons if it didn t then it just wouldn t be oxygen any more. A radioisotope is simply an isotope that is radioactive e.g. carbon 14, which is used in carbon dating.
Introduction to Radioactivity Some substances are classed as radioactive this means that they are unstable and continuously give out radiation: Radiation The nucleus is more stable after emitting some radiation this is called radioactice decay.
Types of radiation Unstable nucleus New nucleus Alpha particle 1) Alpha ( ) an atom decays into a new atom and emits an alpha particle (2 protons and 2 the nucleus of a atom) Beta particle 2) Beta ( ) an atom decays into a new atom by changing a neutron into a and electron. The fast moving, high energy electron is called a particle. Unstable nucleus New nucleus 3) Gamma after or decay surplus is sometimes emitted. This is called gamma radiation and has a very high with short wavelength. The atom is not changed. Unstable nucleus New nucleus Gamma radiation Words frequency, proton, energy, neutrons, helium, beta
Ionisation Radiation is dangerous because it ionises atoms in other words, it turns them into ions by knocking off electrons: Alpha radiation is the most ionising (basically, because it s the biggest). Ionisation causes cells in living tissue to mutate, usually causing cancer.
Blocking Radiation Each type of radiation can be blocked by different materials: Sheet of paper Few mm of aluminium Few cm of lead
Background Radiation 13% are man-made Radon gas Food Cosmic rays Gamma rays Medical Nuclear power
Half life The decay of radioisotopes can be used to measure the material s age. The HALF-LIFE of an atom is the time taken for HALF of the radioisotopes in a sample to decay = radioisotope = new atom formed At start there are 16 radioisotopes After 1 half life half have decayed (that s 8) After 2 half lives another half have decayed (12 altogether) After 3 half lives another 2 have decayed (14 altogether)
A radioactive decay graph Count 1 half life Time
Dangers of radioactivity Alpha Radiation will ionise atoms in living cells this can damage them and cause cancer or leukaemia. Beta Gamma OUTSIDE the body and are more dangerous as radiation is blocked by the skin. INSIDE the body an source causes the most damage because it is the most ionising.
Alexander Litvinenko Timeline of Events Video of risks from polonium 210
Uses of Gamma Radiation Sterilising medical instruments and food Gamma rays can be used to kill and sterilise germs without the need for heating.
Treating Cancer High energy gamma radiation can be used to kill cancerous cells. However, care must be taken in order to enure that the gamma radiation does not affect normal tissue as well. Radioactive iodine can be used to treat thyroid cancer. Iodine is needed by the thyroid so it naturally collects there. Radioactive iodine will then give out beta radiation and kill cancerous cells.
Fuels A fuel is something that can be burned to release heat and light energy. The main examples are: Coal, oil and gas are called fossil fuels. In other words, they were made from fossils.
Using non-renewable fuels in power stations 1) A fossil fuel is burned in the boiler 2) Water turns to steam and the steam drives a turbine 3) The turbine turns a generator 4) The output of the generator is connected to a transformer 5) The steam is cooled down in a cooling tower and reused
Nuclear power stations These work in a similar way to normal power stations: The main difference is that the nuclear fuel is NOT burnt it is used to boil water in a heat exchanger
Nuclear fission More neutrons Neutron Uranium nucleus Unstable nucleus New nuclei (e.g. barium and krypton)
Chain reactions Each fission reaction releases neutrons that are used in further reactions.
Fission in Nuclear power stations These fission reactions occur in the fuel rods and they become very hot. Water cools the rods (which then turns to steam) and the control rods (made of boron) are moved in and out to control the amount of fission reactions taking place.
Disposing of radioactive waste The key to dealing with radioactive waste is to IMMOBILISE it. There are a number of ways of doing this depending on how the waste is: High level waste is immobilised by mixing with making ingredients, melting and pouring the glass into steel containers. Intermediate waste is set in cement in drums. The containers are then kept in stores, often. Words glass, steel, underground, radioactive
Efficiency of Power Stations Heat Heat Heat 100J Boiler 85J Turbine 35J Generator 30J Heat Kinetic Electrical
Other ways of generating electricity Can we drive the turbine directly without burning any fossil fuels?
Wind Power
Hydroelectric Power